Bio test 5 - plants

Explain factors that influence the rate of plant transpiration

-light (warms up the leaf and stimulates opening of the stomata) -temperature -humidity (more drastic concentration gradient when the air is dry) -wind (humid air is replaced by dryer air) -soil water (stomata close to preserve water when there is not enough present in the soil)

Be able to describe the functions of the different meristems.

Apical meristems: are located at the tips of roots to lengthen them quickly and on nodes to grow stems and leaves Floral meristems: produce flower tissue (reproductive organs and petals) Vascular cambium: increases stem thickness Cork cambium: creates a protective layer around the stem

Cambium (Cork, Vascular)

Cambium a meristem that is the site of secondary growth (lateral growth) in conifers and dicots. Vascular cambium is a meristem that forms a layer in between vascular tissue clusters in young dicot stems, producing new layers of xylem and phloem, which results in a thicker stem. Cork cambium is a meristem that creates a protective layer of cork, containing non functioning phloem, around the vascular cambium.

Dermal Tissue

Dermal tissue forms the outermost layer of plants, with the exception of the cuticle, which is an additional waxy layer that protects it. It can be a single layer in young plants, called the epidermis, or very thick in older plants.

Look at a seed and determine how it might be best dispersed based on its structure.

Dispersal by water - Buoyant seeds, like coconuts Seeds that grow up high and can land in the ground Dispersal by animals - fruit → seeds in feces - ants carry seeds - seeds buried in caches - barbed fruit gets caught in fur Dispersal by wind - winged seeds - dandelion "parachute" shape - tumbleweeds - get carried away from parents so there is less competition

Relate a tree's rings to its growth.

Each tree ring is equal to a year in a tree's life. Tree rings form as a result of seasonal growth; growth occurs rapidly in the spring, forming light-colored tissue with thin cell walls. After a while, growth slows and cell walls become thicker, creating a dark layer. Thick rings indicate a year with good weather while thinner rings indicate poor conditions.

Fibrous Root

Fibrous root systems begin as one primary root but grow to be a system of branch roots of the same length extending from the stem's base instead of from other roots. These systems help hold topsoil against heavy rain.

Ground Tissue

Ground tissue is mostly made of parenchyma, cells with thin walls and cytoplasm but big central vacuoles that contain chloroplasts. Collenchyma, tough but flexible cells that help support the plant's organs, and sclerenchyma, which is even tougher, are also found in ground tissue. The function of ground tissue is to make and store sugars and support the whole plant.

Explain why most plants have their stomata on the underside of their leaves

If the stomata were on the tops of the leaves, they would dry out much more quickly, restricting gas exchange and dehydrating the leaf.

Know how leaves exchange gas with the atmosphere and what leaf structure plays a role in that gas exchange.

Leaves "breathe" in carbon dioxide and "breathe" out oxygen when photosynthesizing. After using food, they must do the opposite. Gas is taken in with the opening of the stomata. Air spaces in mesophyll let gas pass between them.

Leaves

Leaves create food through photosynthesis and protect against water loss while still allowing gasses to enter and exit the plant.

Meristem

Meristems can appear at the ends of roots, in stems, and at the beginnings of leaves. Meristems are "regions of unspecialized cells in which mitosis produces new cells that are ready for differentiation." (growth areas in plants). Meristems continue to produce new cells throughout the entirety of a plant's life, meaning that it never stops growing. The two types of meristems are apical (root and shoot) and cambium (lateral growth).

Phloem

Phloem transports dissolved nutrients throughout the plant. It is made of sieve tube elements and companion cells. Both of these cells remain living when they are mature. Sieve tube elements have circular openings on their tops and bottoms to allow for the flow of nutrients. At maturation, most of their organelles, including their nuclei, are lost, and the ones left attach to the cell wall and are sustained by companion cells, which keep all of their organelles. Companion cells also help nutrients to move in and out of the phloem as they support it.

Distinguish between primary and secondary growth.

Primary growth is produced by apical meristems and lengthens stems and roots at the ends of a plant. Secondary growth occurs within stems through cambium and increases stem thickness and strength to better support the plant. It is common in dicots and nonflowering seed plants but almost never occurs in monocots.

Roots

Roots anchor plants, prevent erosion, absorb water and dissolved nutrients, store and transport food, physically hold up the rest of the plant, and have a mutualistic relationship with soil bacteria and fungi that allows them to better absorb materials.

Stems

Stems support plants, transport water and dissolved nutrients up from the roots and bring the products of photosynthesis back down, make leaves and flowers, and provide a defense system against predation and disease.

Taproot

Taproot systems consist of a thick, primary root (the taproot), off of which branch roots extend. Sometimes, taproots store sugars or starches.

Bark

The combination of cork cambium and cork; the outermost, protective layer of a tree trunk.

Osmosis

The diffusion of water through a semipermeable membrane.

Vascular Tissue

The function of vascular tissue is to carry water and nutrients through the plant and support it structurally. It is either xylem or phloem.

Heartwood

The inner layer of old xylem in a tree that does not contain fluid but provides structural support.

Root cap

The root cap is at the very end of a root and protects the meristem. It produces a fluid-like substance that helps the root to slide through the soil. Root caps get worn down quickly and are being constantly renewed by meristems.

Sapwood

The second-innermost layer in tree trunks; active xylem that contains and transports water and nutrients.

Epidermis

The single-cell layer of dermal tissue in young plants.

Understand how guard cells regulate the opening of stomata

The stomata opens when there is a plentiful water supply; water pressure pulls guard cells apart and the stomata opens. When there is little water available, the stomata closes to conserve the water within the plant as the inner walls pull together under a decrease in water pressure.

Explain what transpiration is and why it matters to plants. What is a good thing about transpiration? What is a problem with transpiration?

Transpiration is the loss of water through a plant's leaves. It occurs because, in order to ease the transfer of gasses, mesophyll cells have moist walls that allow water to evaporate easily. In addition the opening of the stomata increases transpiration. Transpiration can be beneficial to leaves by cooling them down. Transpiration is also beneficial because it pulls water in through the roots via cohesion and adhesion, moving water up through the xylem. Transpiration dehydrates leaves and can kill them if there is little water available.

Xylem

Vascular tissue that carries water throughout the plant. Xylem is composed of cells called tracheids and vessel elements. Tracheids are long, thin tubes with tough walls that they leave behind when they die. The lignin in the walls strengthens wood and is water-resistant. Tracheids allow water to either diffuse or flow from one cell to the next via pits and openings, respectively. Vessel elements are stacked vertically, and the walls they leave behind after they die either have small openings to allow water to move in and out or disappear completely. Vessel elements are wider than tracheids.

Diffusion

When molecules at a higher concentration move to an area with a lower concentration until they reach equilibrium.

Source

Where food is created (chloroplasts)

Sink

Where food is stored (ground tissue)

Be able to explain what substance(s) xylem and phloem transport, from what source they transport the substance(s) and where the substance(s) ultimately go.

Xylem transports water up through the plant Phloem transports sugars/dissolves nutrients from source to sink

Know characteristics that distinguish monocots and eudicots.

monocots - one cotyledon in seeds - veins usually parallel in leaves - vascular bundles scattered in stem - fibrous root systems - floral parts usually in multiples of three eudicots - two cotyledon in seeds - veins usually netlike in leaves - taproot - floral parts usually in multiples of five